1. Field of the Invention
The present invention relates to bone implants and, in particular, to a modular dental implant with structure for securing a porous portion to the implant.
2. Description of the Related Art
Dental implants are commonly used as anchoring members for dental restorations to provide prosthetic teeth at one or more edentulous sites in a patient's dentition at which the patient's original teeth have been lost or damaged. Known implant systems include a dental implant made from a suitable biocompatible material, such as titanium. The dental implant is threaded or press fit into a bore which is drilled into the patient's mandible or maxilla at the edentulous site. The implant provides an anchoring member for a dental abutment, which in turn provides an interface between the implant and a dental restoration. The restoration is typically a porcelain crown fashioned according to known methods.
Many current dental implant surgeries are performed in two stages. In the initial or first stage, an incision is made in the patient's gingiva at an edentulous side, and a bore is drilled into the patient's mandible or maxilla at the edentulous site, followed by threading or impacting a dental implant into the bore using a suitable driver. Thereafter, a cap is fitted onto the implant to close the abutment coupling structure of the implant, and the gingiva is sutured over the implant. Over a period of several months, the patient's bone grows around the implant to securely anchor the implant, a process known as osseointegration.
In a second stage of the procedure following osseointegration, the dentist reopens the gingiva at the implant site and secures an abutment and optionally, a temporary prosthesis or temporary healing member, to the implant. Then, a suitable permanent prosthesis or crown is fashioned, such as from one or more impressions taken of the abutment and the surrounding gingival tissue and dentition. In the final stage, the temporary prosthesis or healing member is removed and replaced with the permanent prosthesis, which is attached to the abutment with cement or with a fastener, for example. Alternative single stage implants may be used that extend through the transgingival layer so that the gingiva need not be reopened to access the implant.
One way to improve osseointegration onto the implant, and in turn long term stability of the implant, is to provide a porous material on the implant that the bone can grow into. Such a porous material may also increase short term stability for immediate loading because of its large friction coefficient with surrounding bone. Securing the porous material to the dental implant, however, may be difficult due to the small size and geometry of the device. In general, dental implants are 3 mm to 6 mm in diameter and 4 mm to 16 mm in length. If it is desired for the porous material to only cover a portion of the implant with the remainder being made up of, for example, reinforcing element, threads to compliment initial stability or interface geometry to secure a dental prosthesis, the porous section becomes too small to practically include threads or other securing geometry. Therefore, an implant is desired that includes a locking element to economically secure the porous material in place while allowing for other features such as threads, abutment interface geometry or reinforcing members.